1. Field of the Invention
The present invention relates to a radiation imaging system.
2. Description of the Related Art
Radiation imaging apparatuses are known that capture a radiation image of a subject by irradiating the subject with radiation (for example, X-rays) and detecting the intensity distribution of the radiation that has been transmitted through the subject. Such apparatuses are widely used in the fields of medicine, industry, and the like.
Such imaging generally is performed using a film-screen method for radiation. This method performs imaging through a combination of a photosensitive film and a phosphor having sensitivity to radiation. In this method, a sheet of a rare-earth phosphor that emits light upon irradiation with radiation is held on both faces of a photosensitive film in close contact with them. Radiation that has been transmitted through an object is converted into visible light by means of the phosphor, and the photosensitive film picks up the light. Thereafter, a latent image formed on the film is developed by chemical processing and thus visualized.
On the other hand, with the recent advances in digital technology, a scheme of converting a radiation image into an electrical signal, performing image processing on this electrical signal, and thereafter reproducing the resulting signal on a CRT or the like as a visible image, thus obtaining a high-quality radiation image is becoming widespread. An example of such a method of converting a radiation image into an electrical signal is a technique of temporarily accumulating a radiation transmission image in a phosphor as a latent image, then photoelectrically reading the latent image by irradiating excitation light such as laser light, and outputting the result as a visible image.
Moreover, with the recent advances in semiconductor process technology, apparatuses for capturing a radiation image using a semiconductor sensor are known. This system has a very wide dynamic range as compared with conventional radiation imaging systems that use a photosensitive film, and therefore can provide a radiation image unaffected by variations in the amount of exposure to radiation. Furthermore, unlike the conventional photosensitive film scheme, the need for chemical processing is eliminated, and an output image can be obtained immediately.
X-ray imaging systems will now be described as an example of such radiation imaging systems. Generally, X-ray imaging systems are broadly divided into a stationary type that is installed in a predetermined place, such as an imaging room, and a portable type (a cassette) that can be carried freely. FPDs (flat panel detectors) also have the portable type, which includes an electronic cassette (hereinafter sometimes abbreviated as the cassette), and the race to develop a smaller and lighter electronic cassette is heating up.
In such situation, there is a growing need for the use of a single cassette for a plurality of imaging purposes. For example, when a cassette is used for imaging, generally, imaging is performed with the cassette being placed in an arbitrary position; however, there is a demand for the use of a cassette in a stationary application in which the cassette is installed in a decubitus table or the like. Moreover, this need also includes a demand for an operator himself/herself to be able to perform imaging appropriately according to circumstances without relying on a specially-trained service person. That is to say, the compatibility of a cassette with various X-ray imaging systems at the operator level is beginning to be regarded as important.
In a process of acquiring and outputting an X-ray image, a conventional cassette supplies power to, for example, a semiconductor sensor and various related modules at all times. For this purpose, the cassette is provided with a cable for transmitting power or control signals and is electrically connected to a controller by this cable. The cable is required to have a certain degree of length in order that the cassette can be carried or moved as desired.
However, such a cable may hinder the handling of the electronic cassette, and furthermore, in the case where there is an excess of length, someone may be caught by the cable and fall, and hence the cable, cassette, or controller may be damaged. In particular, in a space, such as an operating room, where surgical treatment is provided, a clean (sterilized) environment is required, and it is necessary to prevent an imaging system including the cable from touching an open (unsterilized) area such as a floor surface.
Here, as disclosed in Japanese Patent Laid-Open Nos. 2003-061942 and 2004-173907, a technique of providing a detachable connector at a lateral end portion of the cassette or in the midst of the cable is known. With this technique, the weight and size of the cassette can be reduced by minimizing the length of the cable connected to the cassette, and thus the portability and the ease of positioning can be improved.
Furthermore, a technique by which the cable connected to the cassette can be connected to a cable connected to the controller via connectors is also known. In the case of this technique, a lock/unlock means is provided at an end of the controller-side cable.
However, with the above-described technique, when the cassette-side connector and the controller-side connector are to be locked/unlocked, it is necessary for the operator to use both hands to perform the operation. Therefore, the operator, for example, temporarily puts the cassette somewhere, thus leaving both hands free to perform the lock/unlock operation of the connectors. In this case, time is taken to make the cassette portable, and therefore, this technique is unsuitable at a scene of urgency, in particular, an emergency scene or the like.
Moreover, there also is a risk of accidental dropping of the cassette, and in this case, the built-in semiconductor sensor may be damaged, or the imaging system or the operator may touch the open (unsterilized) area.